SiC semiconductors have many of the characteristics required by semiconductor devices that operate at high temperatures. Further, SiC semiconductors have superior resistance to breakdown voltage. As a result, there has been vigorous research and development in recent years concerning semiconductor devices utilizing SiC substrates. However, when a metal electrode making contact with a SiC substrate is formed, an energy barrier develops at a boundary surface between the two. The height of the energy barrier is determined by the electron affinity of the SiC substrate, the forbidden band energy gap, and the work function of the metal electrode material. Since SiC semiconductors have an extremely wide forbidden band energy width, the energy barrier at the boundary surface between the electrode and the substrate is high particularly in the case where a metal electrode is formed that makes contact with a p-type SiC substrate. The higher the energy barrier at the boundary surface between the SiC substrate and the metal electrode is, the higher the contact resistance between the two. As a result it is difficult to form an ohmic electrode on a SiC substrate wherein this electrode has low contact resistance with the SiC substrate.
A method is set forth in J. Crofton, et al, “Titanium and aluminum-titanium ohmic contacts to p-type SiC”, Solid-State Electronics, UK, Elsevier Science Ltd, 1997, vol. 41, pp. 1725-1729, wherein a Ti-layer and an Al-layer are formed in sequence on a surface of a SiC substrate, or an alloy layer of Ti and Al is formed and then, as shown in FIG. 15 appended to the present specification, thermal processing is performed at 1000° C. for 2 minutes. With this method, a reaction layer (a Ti3SiC2-layer) is formed on the surface of the SiC substrate. This reaction layer makes ohmic contact with the SiC substrate. It is thus possible, by utilizing the reaction layer, to form an electrode in which the contact resistance is low.